Growing Potatoes in Straw

I live in Reno, NV and planted my seed potatoes in late June. I read the article on Google by Kathee Mierzejewski and everything has worked fine. My potato plants are now very high with lots of flowers but I don't see any 'new' potatoes. It rained for 10 days straight after I planted them and some dirt fell over the seed potatoes. Should I dig down to find the potatoes? I dug a small way with my hands but couldn't find any potatoes. Should I wait longer before I try to get potatoes, and will they be buried in the dirt? I am assuming they grow down into the dirt. As you can tell, I am new at this and don't want to just 'rip up' a plant looking for potatoes.